Age from birthdate in python

Question

How can I find an age in python from today s date and a persons birthdate  The birthdate is a from a DateField in a  Django model

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If you re looking to print this in a page using django templates  then the following might be enough      birth date timesince

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from datetime import date  def age birth date       today   date today       y   today year - birth date year     if today month  lt  birth date month or today month    birth date month and today day  lt  birth date day          y -  1     return y

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Extend to Danny W  Adair Answer  to get month also  def calculate age b       t   date today       c     t month  t day   lt   b month  b day       c2    t day lt  b day      return t year - b year - c c 12 t month-b month-c2

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The classic gotcha in this scenario is what to do with people born on the 29th day of February  Example  you need to be aged 18 to vote  drive a car  buy alcohol  etc     if you are born on 2004-02-29  what is the first day that you are permitted to do such things  2022-02-28  or 2022-03-01  AFAICT  mostly the first  but a few killjoys might say the latter   Here s code that caters for the 0 068   approx  of the population born on that day   def age in years from date  to date  leap day anniversary Feb28 True       age   to date year - from date year     try          anniversary   from date replace year to date year      except ValueError          assert from date day    29 and from date month    2         if leap day anniversary Feb28              anniversary   datetime date to date year  2  28          else              anniversary   datetime date to date year  3  1      if to date  lt  anniversary          age -  1     return age  if   name         main         import datetime      tests            2004  2 28 2010  2 27  5 1     2004  2 28 2010  2 28  6 1     2004  2 28 2010  3  1  6 1      2004  2 29 2010  2 27  5 1     2004  2 29 2010  2 28  6 1     2004  2 29 2010  3  1  6 1      2004  2 29 2012  2 27  7 1     2004  2 29 2012  2 28  7 1     2004  2 29 2012  2 29  8 1     2004  2 29 2012  3  1  8 1      2004  2 28 2010  2 27  5 0     2004  2 28 2010  2 28  6 0     2004  2 28 2010  3  1  6 0      2004  2 29 2010  2 27  5 0     2004  2 29 2010  2 28  5 0     2004  2 29 2010  3  1  6 0      2004  2 29 2012  2 27  7 0     2004  2 29 2012  2 28  7 0     2004  2 29 2012  2 29  8 0     2004  2 29 2012  3  1  8 0               for line in tests splitlines            nums    int x  for x in line split            if not nums              print             continue         datea   datetime date  nums 0 3           dateb   datetime date  nums 3 6           expected  anniv   nums 6 8          age   age in years datea  dateb  anniv          print datea  dateb  anniv  age  expected  age    expected   Here s the output   2004-02-28 2010-02-27 1 5 5 True 2004-02-28 2010-02-28 1 6 6 True 2004-02-28 2010-03-01 1 6 6 True  2004-02-29 2010-02-27 1 5 5 True 2004-02-29 2010-02-28 1 6 6 True 2004-02-29 2010-03-01 1 6 6 True  2004-02-29 2012-02-27 1 7 7 True 2004-02-29 2012-02-28 1 7 7 True 2004-02-29 2012-02-29 1 8 8 True 2004-02-29 2012-03-01 1 8 8 True  2004-02-28 2010-02-27 0 5 5 True 2004-02-28 2010-02-28 0 6 6 True 2004-02-28 2010-03-01 0 6 6 True  2004-02-29 2010-02-27 0 5 5 True 2004-02-29 2010-02-28 0 5 5 True 2004-02-29 2010-03-01 0 6 6 True  2004-02-29 2012-02-27 0 7 7 True 2004-02-29 2012-02-28 0 7 7 True 2004-02-29 2012-02-29 0 8 8 True 2004-02-29 2012-03-01 0 8 8 True

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That can be done much simpler considering that int True  is 1 and int False  is 0   from datetime import date  def calculate age born       today   date today       return today year - born year -   today month  today day   lt   born month  born day

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import datetime   Todays date  td datetime datetime now   date      Your birthdate  bd datetime date 1989 3 15    Your age  age years int  td-bd  days  365 25

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The simplest way is using python-dateutil  import datetime  import dateutil  def birthday date         Get the current date     now   datetime datetime utcnow       now   now date          Get the difference between the current date and the birthday     age   dateutil relativedelta relativedelta now  date      age   age years      return age

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Here is a solution to find age of a person as either years or months or days   Lets say a person s date of birth is 2012-01-17T00 00 00 Therefore  his age on 2013-01-16T00 00 00 will be 11 months  or if he is born on 2012-12-17T00 00 00   his age on 2013-01-12T00 00 00 will be 26 days  or if he is born on 2000-02-29T00 00 00  his age on 2012-02-29T00 00 00 will be 12 years  You will need to import datetime   Here is the code   def get person age date birth  date today        At top level there are three possibilities   Age can be in days or months or years  For age to be in years there are two cases  Year difference is one or Year difference is more than 1 For age to be in months there are two cases  Year difference is 0 or 1 For age to be in days there are 4 possibilities  Year difference is 1 20-dec-2012 - 2-jan-2013                                                    Year difference is 0  Months difference is 0 or 1     years diff   date today year - date birth year months diff   date today month - date birth month days diff   date today day - date birth day age in days    date today - date birth  days  age   years diff age string   str age      years     age can be in months or days  if years diff    0      if months diff    0          age   age in days         age string   str age      days      elif months diff    1          if days diff  lt  0              age   age in days             age string   str age      days          else              age   months diff             age string   str age      months      else          if days diff  lt  0              age   months diff - 1         else              age   months diff         age string   str age      months    age can be in years  months or days  elif years diff    1      if months diff  lt  0          age   months diff   12         age string   str age      months           if age    1              if days diff  lt  0                  age   age in days                 age string   str age      days           elif days diff  lt  0              age   age-1             age string   str age      months      elif months diff    0          if days diff  lt  0              age   11             age string   str age      months          else              age   1             age string   str age      years      else          age   1         age string   str age      years    The age is guaranteed to be in years  else      if months diff  lt  0          age   years diff - 1     elif months diff    0          if days diff  lt  0              age   years diff - 1         else              age   years diff     else          age   years diff     age string   str age      years   if age    1      age string   age string replace  years    year   replace  months    month   replace  days    day    return age string   Some extra functions used in the above codes are   def get todays date                This function returns todays date in proper date object format             return datetime now     And  def get date format str date       This function converts string into date type object     str date   str date split  T   0  return datetime strptime str date    Y- m- d     Now  we have to feed get date format   with the strings like 2000-02-29T00 00 00  It will convert it into the date type object which is to be fed to get person age date birth  date today    The function get person age date birth  date today  will return age in string format

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As I did not see the correct implementation  I recoded mine this way         def age in years from date  to date datetime date today       if  DEBUG       logger debug  def age in years from date   s   to date   s       from date  to date      if  from date gt to date     swap when the lower bound is not the lower bound     logger debug  Swapping dates           tmp   from date     from date   to date     to date   tmp    age delta   to date year - from date year   month delta   to date month - from date month   day delta   to date day - from date day    if  DEBUG       logger debug  Delta s are    i     i    i      age delta  month delta  day delta      if  month delta gt 0  or  month delta  0 and day delta gt  0         return age delta     return  age delta-1    Assumption of being  18  on the 28th of Feb when born on the 29th is just wrong  Swapping the bounds can be left out     it is just a personal convenience for my code

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from datetime import date  def calculate age born       today   date today       try           birthday   born replace year today year      except ValueError    raised when birth date is February 29 and the current year is not a leap year         birthday   born replace year today year  month born month 1  day 1      if birthday  gt  today          return today year - born year - 1     else          return today year - born year   Update  Use Danny s solution  it s better

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Unfortunately  you cannot just use timedelata as the largest unit it uses is day and leap years will render you calculations invalid   Therefore  let s find number of years then adjust by one if the last year isn t full   from datetime import date birth date   date 1980  5  26  years   date today   year - birth date year if  datetime now   - birth date replace year datetime now   year   days  gt   0      age   years else      age   years - 1   Upd   This solution really causes an exception when Feb  29 comes into play   Here s correct check   from datetime import date birth date   date 1980  5  26  today   date today   years   today year - birth date year if all  x  gt   y  for x y in zip today timetuple    birth date timetuple        age   years else     age   years - 1   Upd2   Calling multiple calls to now   a performance hit is ridiculous  it does not matter in all but extremely special cases   The real reason to use a variable is the risk of data incosistency

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As suggested by   Tomasz Zielinski  and  Williams python-dateutil can do it just 5 lines   from dateutil relativedelta import   from datetime import date today   date today   dob   date 1982  7  5  age   relativedelta today  dob    gt  gt relativedelta years  33  months  11  days  16

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You can use Python 3 to do all this  Just run the following code and see    Creating a variables   greeting    quot Hello   quot  name   input  quot what is your name  quot   birth year   input  quot Which year you were born  quot   response    quot Your age is  quot     Converting string variable to int   calculation   2020 - int birth year       Printing   print f  greeting  name    response  calculation

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from datetime import date  days in year   365 2425     age   int  date today   - birth date  days   days in year    In Python 3  you could perform division on datetime timedelta   from datetime import date  timedelta  age    date today   - birth date     timedelta days 365 2425

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Slightly modified Danny s solution for easier reading and understanding      from datetime import date      def calculate age birth date           today   date today           age   today year - birth date year         full year passed    today month  today day   lt   birth date month  birth date day          if not full year passed              age -  1         return age

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import datetime  def age date of birth       if date of birth  gt  datetime date today   replace year   date of birth year           return datetime date today   year - date of birth year - 1     else          return datetime date today   year - date of birth year   In your case   import datetime    your model def age self       if self birthdate  gt  datetime date today   replace year   self birthdate year           return datetime date today   year - self birthdate year - 1     else          return datetime date today   year - self birthdate year

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Expanding on Danny s Solution  but with all sorts of ways to report ages for younger folk  note  today is datetime date 2015 7 17     def calculate age born                   Converts a date of birth  dob  datetime object to years  always rounding down          When the age is 80 years or more  just report that the age is 80 years or more          When the age is less than 12 years  rounds down to the nearest half year          When the age is less than 2 years  reports age in months  rounded down          When the age is less than 6 months  reports the age in weeks  rounded down          When the age is less than 2 weeks  reports the age in days              today   datetime date today       age in years   today year - born year -   today month  today day   lt   born month  born day       months    today month - born month -  today day  lt  born day    12     age   today - born     age in days   age days     if age in years  gt   80          return 80   years or older      if age in years  gt   12          return age in years   years      elif age in years  gt   2          half    and a half   if months  gt  6 else            return age in years    syears  half     elif months  gt   6          return months   months      elif age in days  gt   14          return age in days 7   weeks      else          return age in days   days    Sample code   print   d  s   calculate age datetime date 1933 6 12      gt  80 years print   d  s   calculate age datetime date 1963 6 12      gt  12 years print   d  s   calculate age datetime date 2010 6 19      gt  2 years print   d  s   calculate age datetime date 2010 11 19      gt  2 years with half print   d  s   calculate age datetime date 2014 11 19      gt  6 months print   d  s   calculate age datetime date 2015 6 4      gt  2 weeks print   d  s   calculate age datetime date 2015 7 11     days old  80 years or older 52 years 5 years 4 and a half years 7 months 6 weeks 7 days

[python] Age from birthdate in python

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